1. Field of the Invention
The present invention relates generally to methods and compositions for stimulating carbon nutrient uptake that yields enhanced growth in plants with improved water use efficiency.
Photosynthesis is the process by which all photosynthetic plants utilize solar energy to build carbohydrates and other organic molecules from carbon dioxide (CO.sub.2) and water. The conversion of CO.sub.2 into plant matter is generally referred to as carbon fixation and occurs by the C.sub.3 cycle in most plants. Plants in which the C.sub.3 cycle occurs are referred to hereinafter as "C.sub.3 plants". The C.sub.3 cycle involves the carboxylation of ribulose-1,5-bisphosphate (RuBP) to produce two molecules of the 3-carbon compound, 3-phosphoglyceric acid (PGA), the carbon skeleton for hexoses and other organic molecules. An important aspect of the C.sub.3 cycle is that the RuBP pool remains charged during carbon uptake. Therefore, for every six carboxylation events, which yields twelve PGA's, two PGA's can be converted to hexose, while ten molecules of PGA are recycled to replace the six RuBP's initially carboxylated. A simplified illustration of the C.sub.3 cycle is shown in FIG. 1.
Another event in the C.sub.3 cycle shown in FIG. 1, is photorespiration, during which oxygen (O.sub.2) outcompetes CO.sub.2 and is added to RuBP. As a result of oxidation, phosphoglycolate is formed. The phosphoglycolate is dephosphorylated to glycolate which is oxidized to glyoxylate. Glycine is made by attachment of ammonia (NH.sub.3). The glycine is deaminated releasing NH.sub.3 and further decarboxylated to CO.sub.2 plus a single carbon (C.sub.1) fragment. This C.sub.1 fragment from glycine is passed on to a FORMYLTETRAHYDROPTEROYLPOLYGLUTAMATE (C.sub.1 -THF) pool, whereby, it is catalytically transferred in the form of 5,10-methylenetetrahydrofolate. Serine hydroxymethyltransferase (SHMT), an abundant enzyme of the C.sub.1 -THF pool, reversibly catalyzes the attachment of a second molecule of glycine with the C.sub.1 fragment to make serine. Photorespiration is a source of glyoxylate which is ultimately cleaved into C.sub.1 fragments.
The amination of glyoxylate and deamination of glycine during photorespiration occurs through the GOGAT (glutamine: 2-oxo-glutarate amino transferase) cycle. The GOGAT cycle is the path by which NH.sub.3 is assimilated by plants and follows the depiction given in FIG. 2, wherein, glutamine: 2-oxo-glutarate amino transferase catalyzes the combining of glutamine with 2-oxo-glutarate to form two molecules of glutamate. In the course of photorespiration, one molecule of glutamate can provide NH.sub.3 for amination of glyoxylate to form glycine, while the other is recycled and combines with the NH.sub.3 released when glycine is deaminated, as shown in FIG. 2. In another energy consuming process, the serine formed must be recycled back to the RuBP pool for further carboxylations, otherwise photorespiration would drain the RuBP pool. Recycling serine to PGA involves an amino transfer from serine to glyoxylate to form glycine. The resulting 1-hydroxypyruvate is reduced to glycerate and then phosphorylated to form PGA. The PGA can be recycled back to RuBP. The energy intensive process of photorespiration depletes C.sub.2 and releases CO.sub.2 but salvages 75% of the carbons in the glycolate produced.
Conventional plant nutrient formulations have been directed at the delivery of recognized macro- and micronutrients, but have not generally included a carbon source intended to enhance carbon dioxide fixation by the C.sub.3 cycle or otherwise, as defined by Hawkes et al. (1985) Western Fertilizer Handbook, The Interstate Publishers, Danville, Ill., Pp. 288. Fertilizers for higher plants generally include nitrogen, phosphorus, and potassium, which are referred to as macronutrients. Fertilizers often include other minerals and micronutrients, such as, iron, sulfur, calcium, and magnesium, which may support growth if there is a deficiency; but they are not utilized to target enhancement of catalysts that would divert from conventional pathways. The use of conventional fertilizers to enhance plant growth via the C.sub.3 cycle is inefficient and incomplete because photosynthesis under normal atmospheric conditions is CO.sub.2 -limited and light-limited. A fertilizer that provides carbon, enhances uptake of carbon, or increases the efficiency of carbon metabolism would increase growth. Conventional fertilizers do not directly provide carbon as a nutrient nor do they improve carbon fixation even though carbon accounts for 80% or more of plant growth under the conventional C.sub.3 cycle. Because of their imbalances, application of conventional fertilizers has never achieved optimal productivity during photorespiration.
For these reasons, it would be desirable to provide improved methods and formulations for promoting plant growth. It would be particularly desirable if such methods and compositions were able to maintain flows of C.sub.1 fragments which enhance growth without toxicity. The present invention should further provide convenient methods resulting in increased photosynthesis for applying the compositions to photosynthetic plant surfaces. Additionally, it would be desirable if the methods and compositions of the present invention could promote rapid growth and maturing of the treated plant, increase sugar content and, otherwise, increase the quality of the plant, all the while, adjusting transpiration to reduce the watering requirement of the plant and enhance environmental tolerance.
2. Description of the Background Art
Study of the path of carbon in photosynthesis four decades ago (A. A. Benson (1951) "Identification of Ribulose in .sup.14 CO.sub.2 Photosynthesis Products" J. Am. Chem. Soc. 73:2971; J. R. Quayle et al. (1954) "Enzymatic Carboxylation of Ribulose Diphosphate" J. Am. Chem. Soc. 76:3610) revealed the nature of the CO.sub.2 fixation process in plants. The metabolism of one-carbon compounds other than CO.sub.2 had been examined, and methanol was found to be utilized by algal strains of Chlorella and Scenedesmus for sugar and amino acid production as rapidly as CO.sub.2. Since both types of early experiments were performed with substrate on a tracer scale, it was neither clear that the rates were comparable nor what the pathway for methanol conversion to sucrose involved. A subsequent publication on the subject (E. A. Cossins (1964) "The Utilization of Carbon-1 Compounds by Plants" Canadian. J. Biochem. 42:1793) reported that plants metabolize methanol to CO.sub.2, glycerate, serine, methionine, and other sugar or structural precursors rapidly. The conclusion that methanol is readily oxidized to formaldehyde and converted to fructose-6-phosphate has been reported in bacteria (C. L. Cooney and D. W. Levine (1972) "Microbial Utilization of Methanol" Adv. Appl. Microbiol. 15:337) and fungi (W. Harder et al. (1973) "Methanol Assimilation by Hyphomicrobium sp." J. Gen. Microbiol. 78:155). Based on these studies of microorganisms it was concluded that formaldehyde condenses with pentose-5-phosphate to yield allulose-6-phosphate which epimerizes to fructose-6-phosphate.
C.sub.1 metabolism in higher plants is discussed in Cossins, "One-carbon Metabolism", The Biochemistry of Plants, Vol. 2, Ch. 9, Pp. 365-418, Academic Press, Inc., 1980, and in Cossins, "Folate Biochemistry and the Metabolism of One-Carbon Units," The Biochemistry of Plants, Vol. 11, Ch. 9, Academic Press, Inc., 1987. In his review of photorespiration, W. L. Ogren (1984), "Photorespiration: Pathways, Regulation, and Modification." Ann. Rev. Physiol. 35:415-442, concludes that accumulation of glycolate inhibits plant growth; and furthermore, chemical or genetic inhibition of the glycolate pathway leads to plant death.
Additions of folic acid, pteroic acid, methyltetrahydrofolate and folinate to root cell culture nutrient medium, as described by P. Crosti, M. Malerba and R. Bianchetti (1993) "Growth-dependent changes of folate metabolism and biosynthesis in cultured Daucus-carota cells," Plant Science 88(1):97-106, shows that growth was inhibited by folinate, aminopterin, methotrexate and sulfanilamide; and even though initial rates of growth were stimulated by folic acid, inhibited by pteroic acid, or were unaffected by methyltetrahydrofolate, the final growth yield was no different from the untreated control in any case.
J. Killmer, Ph.D. Thesis entitled Growth of Cultured Carrot Cells as Affected by Glyphosate, Asulam, and Various Plant Metabolites, University of Illinois, Urbana-Champaign, 1980, describes the effect of metabolites, including p-aminobenzoic acid (pABA) and folate, when applied to plants together with the herbicide glyphosate. Both pABA and folate were applied to plants as controls with no effect on growth being observed.
Foliar fertilizers containing calcium formate are described in Japanese Patent Publication 59-137384. U.S. Pat. No. 3,897,241 describes application of ethanolamine formulations with carboxylic acids of less than 8 carbons, such as, oxalic acid, formic acid, acetic acid, phthalic acid and glutaric acid to fruit-bearing plants 10 to 150 days prior to ripening. European Patent 465 907 A1 describes compositions for stimulating the growth and ripening of plants comprised of at least one adduct of menadione bisulfite and a compound chosen from a group including pABA. U.K. Patent Application 2 004 856 describes plant growth stimulating compositions consisting of cysteine as the active component in formulations that also include folic acid, an aldehyde, a magnesium salt, and a buffer. U.S. Pat. No. 4,405,531, discloses the novel derivatives of N-phosphonomethylglycine used as phytotoxicants and herbicides. USSR application 816437 describes the spraying of cucumber leaves with glutamic acid to accelerate fruit maturation and increase crop yield. Lawyer et al. (1983) Plant Physiol. 72:420-425 describes glutamate addition to chloroplasts having no effect on net photosynthesis of chloroplasts, but increasing .sup.14 CO.sub.2 incorporation on addition to isolated spinach cells; furthermore, they also concluded, that treatment with sodium glyoxylate inhibits photosynthesis. Grassi et al. (1992) Rev. Agric. 67:89-95, describes the foliar application of amino acids to enhance the growth of soybeans. Aono et al. (1982) Chagyo Gijutsu Kenkyu 63:23-32, describes the spraying of tea plants with vitamins and amino acids to enhance yield. Kazaryan et al. (1989) Biol. Zh. Ann. 42:177-181, describes the foliar spray of glycine to induce auxin and growth inhibitor production in nitrogen-deprived plants. Chinese patent application 1046886 describes plant leaf fertilizers including amino acids.
Methanol and other alcohols have been included in certain prior fertilizer formulations for various purposes. U.S. Pat. No. 3,918,952, discloses the incorporation of 1-15 parts by volume lower alcohol in clear liquid fertilizers as stability enhancers. U.S. Pat. No. 4,033,745, discloses the incorporation of 0.05% to 1% alcohol in liquid fertilizers as a stability enhancer. U.S. Pat. Nos. 4,409,015 and 4,576,626 describe the addition of alcohols to fertilizers to enhance solubilization of phospholipids. See also Hungarian patent abstract T45468 and USSR patent abstract 84-3794472, which describes the incorporation of methanol into fertilizers at unspecified concentrations.
British patent application 2 185 472 A describes foliar plant feeding compositions which comprise from 2% to 4% by weight of protein hydrolysate including amino acids, polypeptides, and oligopeptides. Particular amino acids are not identified. The application of oxamide (H.sub.2 N--CO--CO--NH.sub.2) in foliar sprays to wheat and soy as a slow-release of nitrogen source is described in Schuler and Paulsen (1988) J. Plant Nutr. 11:217-233. The foliar application of radiolabeled proline to wheat is described in Pavlova and Kudrev (1986) Dolk. Bolg. Akad. Nauk. 39:101-103. Barel and Black (1979) Agron. J. 71:21-24 describes foliar fertilizers incorporating polyphosphate compounds combined with a surfactant (0.1% Tween.RTM. 80). U.S. Pat. No. 4,863,506, describes the incorporation of L-(d)-lactic acid in foliar sprays where the lactic acid is alleged to act as a growth regulator. U.S. Pat. No. 4,799,953, describes polymeric condensates of the sulfur-polymers, thiolactic and thioglycolic acids, increasing the rate of growth and chlorophyll specific to tissue and hydroponic culture of Lemna minor.
The degradation of formamidine-derivative insecticides in plants has been variously described by C. O. Knowles (1970) J. Agr. Food Chem. 18:1038-1047 for chlordimeform; C. D. Ercegovich, S. Witkonton and D. Asquith (1972) ) J. Agr. Food Chem. 20:565-568 and A. K. Sen Gupta and C. O. Knowles (1986) J. Agr. Food Chem. 17:595-600 for chlordimeform and formetanate. R. T. Meister (1995) Editor-in-Chief, Farm Chemicals Handbook, Meister Publishing Co., Willoughby, OH, describes several commercial formamidine insecticides.
R. T. Meister, supra, describes limited use of phthalates as pesticides; for example, European Patent 244,754/EP was granted for herbicides emulsified in water-immiscible mixtures that can include a phthalate; U.S. Pat. No. 4,594,096 describes pesticides containing alkyl phthalate as a solvent; U.S. Pat. No. 3,891,756 describes pesticidal compositions that contain a starchy biopolymer, a carbonate and an organic acid, among which phthalic acid was included. Root treatments of phthalate derivatives for iron deficiency is described in a research series by S. Kanan, for example, S. Kanan (1986) J. Plant Nutrition 9(12):1543-1551, shows phthalic acid and dibutyl phthalate can reverse chlorosis in sorghum.
PCT W094/00009 is the published text of parent application PCT/US93/05673 (published on Jan. 6, 1994). South African patent 93/4341, which is also the equivalent of PCT/US93/05673, issued on Mar. 30, 1994.